Thermoplastic resins, particularly high performance plastics with excellent mechanical properties and good heat resistance, are used in various applications. For example, polyamide resins and polyester resins are suitable for use in the manufacture of a variety of industrial parts, including electrical/electronic parts, machine parts and automotive parts, mainly by injection molding due to their good balance of mechanical properties and toughness. Polyester resins, particularly polybutylene terephthalate and polyethylene terephthalate, with excellent moldability, heat resistance, mechanical properties, and chemical resistance are widely used as materials for industrial molded articles such as connectors, relays, and switches of automobiles and electrical/electronic devices. Amorphous resins such as polycarbonate resins are highly transparent and dimensionally stable. Due to these advantages, amorphous resins are used in many fields, including optical materials and parts of electric appliances, OA equipment, and automobiles.
Electrical/electronic parts should be prevented from malfunction caused by static electricity and contamination by dirt. For this purpose, electrical/electronic parts are required to have antistatic properties. Automobile fuel pump parts are also required to have high electrical conductivity in addition to existing physical properties.
Additives such as surfactants, metal powders and metal fibers are generally used to impart electrical conductivity to resins. However, these additives tend to deteriorate the physical properties (such as conductivity and mechanical strength) of final molded articles.
Conductive carbon black is a common material for imparting conductivity to resins. However, the addition of a large amount of carbon black is necessary to achieve high electrical conductivity and the structure of carbon black also tends to decompose during melt mixing. The resulting resins suffer from poor processability and considerable deterioration in thermal stability and other physical properties.
Under these circumstances, research has concentrated on resin composites including carbon nanotubes instead of conductive carbon black in order to achieve improved conductivity while reducing the amount of conductive fillers added.